A code division multiple access (CDMA) cellular communication system normally has several radio frequency (RF) carriers. Each RF carrier is considered a resource for serving incoming calls. The incoming calls or the calls in progress served by a system resource is the load of that resource. Each resource has a load capacity.
The communication system may have a total loading capacity far more than what is required to maintain an optimum Frame Error Rate (FER) on all channels. Because the total load capacity may not be distributed evenly among all the RF carriers, or the RF carriers may be loaded unevenly, the FER is degraded for at least a period of time every time a new call is established on a carrier having a load level that is marginal for maintaining an optimum Frame Error Rate (FER). Other carriers may be available, however, which have an acceptable margin between the load level and the load capacity. As a result, an imbalance in loading capacity between RF carriers creates an environment for inefficient utilization of the total system loading capacity.
One suggestion to control loading of a system has been to load the carriers based on a ranking. The ranking of the carriers is based on the availability of resources and the load level of each carrier. For example, the best candidate is selected according to a minimum amount of load and the maximum amount of resources available for processing an incoming call. However, the initial control of a call setup on a carrier does not just effect that particular carrier per se; its effect uncontrollably propagates to carriers on the adjacent cells and sectors of the communication system.
For example, Interim Standard (IS)-95 CDMA communication standard, published by the Telecommunications Industry Association in Washington, DC, along with subsequent revisions thereof, requires the communication system to establish links on some of the adjacent cells or sectors for soft hand-offs. If the RF carrier load level in the adjacent cells or sectors is marginal with respect to its load capacity, these uncontrollable RF carrier assignments on adjacent cells or sectors may cause severe FER degradation. Thus, although a controlled method of initial call set up is devised, its effect on the RF carriers in the adjacent cells and sectors of the communication systems could be uncontrollable.
Therefore, there is a need to efficiently utilize the total loading capacity of a system when an imbalance of loading capacity exists among RF carriers, sectors or cells of the communication system.